This invention relates to a horizontal cylinder arrangement for an internal combustion engine, and more particularly to a horizontal cylinder arrangement in a four-cycle internal combustion engine in which the pistons are supported for horizontal reciprocation and wherein the pistons have a ring structure for positioning and maintaining the gaps of the piston rings out of the area below the piston axis.
It is common practice to provide the pistons of internal combustion engines with one or more piston rings that are placed in the cylinder and fitted into corresponding grooves formed around the outer peripheries of the pistons. Most engines employ two types of piston rings. One or two compression rings for each piston are typically employed for maintaining compression pressures in the combustion chambers by preventing the combustion gases from leaking out of the combustion chambers and into the crankcase chamber. An oil ring is normally employed in connection with each piston to scrape oil from the inner surface of the cylinders and to prevent the oil in the crankcase chamber from leaking into the combustion chambers. Each type of ring has ends which form a gap when it is placed in the cylinders and fitted in the piston grooves.
Although this type of piston assembly is generally satisfactory, the gaps in the compression rings can create a problem in some internal combustion engine cylinder arrangements, particularly in engines formed with horizontally disposed cylinder bores wherein the pistons reciprocate in the horizontal direction. In particular, there has been a problem in this type of engine arrangement in maintaining the compression ring end gaps out of the area on the outer surfaces of the pistons just below the piston axis.
The reason for this is that during operation of engines formed with horizontally disposed cylinder bores, the weight balance of the rings around the pistons has a tendency to cause the rings and ring end gaps to move circumferentially within their respective grooves and align themselves along the outer surface of their respective piston just under the piston axis in a position in which the rings are quite stable. When this occurs, there is a distinct possibility that any unburned fuel charge in the combustion chambers will flow along the lower inner surface of the cylinder bore through these gaps and into the crankcase chamber. If this unburned fuel charge enters the crankcase chamber, it will dilute and contaminate the oil which is used to lubricate the engine and hence will reduce the lubricating effectiveness of the oil.
This problem is even more likely to occur where the horizontally supported pistons are provided with only one piston ring each which is of the compression ring type. In this case, any unburned fuel charge in the combustion chambers will be able to enter the crankcase chamber through the associated compression ring end gap as soon as that ring is positioned under the piston axis.
It is, therefore, a principal object of this invention to provide a piston ring structure for a four-cycle internal combustion engine which prevents any unburned fuel charge in the combustion chamber from entering the crankcase chamber.
It is another object of this invention to provide a piston ring structure for a four-cycle internal combustion engine wherein the compression ring end gap of each compression ring is positioned and maintained on the outer periphery of the respective piston outside of the area under the piston axis.